Well, I can always be
wrong, Bill. However, more air mass flow at the same rpm (due to
“theoretical” better flow, i.e. Better volumetric efficiency) would mean the
EC2 would see higher manifold pressure and should respond by enrichening the
mixture to match – I mean that is what the EC does- match fuel flow to
manifold pressure. Now you would think that if it matched the higher
manifold pressure accurately then while more fuel would be flowing – the
air/fuel ratio (which is what we are looking at on our indicator) should
theoretically remain the same. Could be the EC “over compensated” ?
Perhaps another way
of looking at is with the old muffler which gave a certain manifold pressure
at rpm X would then point to the corresponding manifold pressure bin in the
EC2 MCT. Now if at the same rpm with the new muffler the airflow mass
flow is greater - then the manifold pressure at X rpm will be corresponding
greater. Since the EC2/3 is using manifold pressure to point to the
correct bin – it is now pointing a couple of bins higher in the map.
Normally the higher you are in the map the more fuel is signaled to
flow. So Mike would then have to “re-adjust” the MCT table to match the
new volumetric efficiency increase.
Now if the new
muffler was producing more back pressure then the airflow would be lower for
the same RPM or the Volumetric efficiency would be somewhat worst than the
with the old muffler. So if the lower air mass flow corresponds to a
lower manifold pressure then the EC2 should be point a couple of bins lower in
the MCT which normally would signal less fuel is required and injected to
match the lower air flow.
Or at least that is
my take on it.
Perhaps Tracy is loafing around
today {:>) and will come on line the real
explanation.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Sunday, September 06, 2009 8:45
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: DNA
muffler
Ed,
We are on opposite sides of this possibility.
Seems that if there were more air allowed, the mixture would lean, not
richen. This is exactly what I was thinking when I suggested that the
muffler might cause more back pressure, lower the air flow, and cause
richness.???
What I may be missing is just what the EC-2/3 would do
if it saw a certain condition. Explain,
please.
Bill B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Sunday, September 06, 2009 8:20
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: DNA
muffler
Hi
Mike,
Interesting reaction
of engine to your DNA muffler. A possible explanation for richer across
the board. It appears that the DNA muffler may offer less back pressure
to the engine meaning you get more air into the engine at any given rpm.
That could increase your manifold pressure and drive the EC2 to enrichen the
mixture to compensate. The reason the top end rpm may not change is that
at that point there is some other restriction such as the intake, TB, etc that
may come into play. Just a theory of
course.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mike Wills
Sent: Saturday, September 05, 2009 11:47
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] DNA
muffler
Received my DNA muffler this past
week and got it installed and running. Havent flown it yet, but have done some
taxi and full power runups. So far I'm a little disappointed. It doesnt appear
to be any quieter than my home made muffler. I'll reserve judgement until I
actually fly it, but from the cockpit the noise level seems the same, and my
buddy standing about 50 ' away said he thought the noise level was the
same.
One thing not the same - the
muffler screwed up my tuning. It appears to be considerably richer now all
across the RPM range. And the big bog at the staging point that took me so
long to tune out is back with a vengeance. Oddly, in spite of the tune issues
it still appears to reach the same static RPM as
previously.
Looks like the solution for
me is going to be the high $ headset and the rest of the world is just going
to have to live with it.
__________ Information from ESET NOD32
Antivirus, version of virus signature database 3267 (20080714)
__________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
__________ Information from ESET NOD32
Antivirus, version of virus signature database 3267 (20080714)
__________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com